In the episode when Lisa talks about the Curies dying of radiation poisoning. She says BOTH Pierre and Marie died of radiation poisoning. Only Marie died of radiation poisoning, Pierre was killed when he was struck by a horse-drawn carriage, not radiation poisoning. I forgot which episode it was, but I just remember that after she said that, Bart imagined the Curies in his mind as giants surrounded by green stuff and red beams coming from their eyes.